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Sweden began research into nuclear energy in 1947 with the establishment of the Atomic Energy Company, which originated in the ongoing military research and development at the Defence Institute FOA.〔T. Jonter: Nuclear Weapon Research in Sweden. The Co-operation Between Civilian and Military Research, 1947-1972, SKI Report 02:18〕 In 1954, the country built its first small research heavy water reactor. It was followed by two heavy water reactors: Ågesta, a small heat and power reactor in 1964, and Marviken which was finished but never operated, due to several safety issues.〔Jonter ibid〕 Both were heavy water reactors, motivated by the option to use Swedish uranium without isotope enrichment. The option to use plutonium from power reactors was closed only in 1968 with the signing of the Non-Proliferation Treaty. The switch to light water reactors started a few years earlier with Oskarshamn 1. Six nuclear reactors began commercial service in the 1970s, another six through 1985, with one unit closed in 1999 and another in 2005. Nine of the reactors were designed by ASEA, three supplied by Westinghouse. Sweden has three operational nuclear power plants, with ten operational nuclear reactors, which produce about 35-40% of the country's electricity.〔http://pris.iaea.org/public/, see Sweden〕 The nation's largest power station, Ringhals Nuclear Power Plant, has four reactors and generates about 15 percent of Sweden's annual electricity consumption.〔(Vattenfall - QuickLink )〕 The power plants in Forsmark and Oskarshamn each have three reactors. Sweden formerly had a nuclear phase-out policy, aiming to end nuclear power generation in Sweden by 2010. On 5 February 2009, the Government of Sweden announced an agreement allowing for the replacement of existing reactors, effectively ending the phase-out policy. ==Chronology== Electricity production in Sweden is dominated by nuclear power and hydroelectricity which currently make about equal contributions to energy production, for which demand has remained fairly constant since 1990. On 1 May 1969, a prototype nuclear cogeneration plant outside Stockholm, Ågestaverket (R3) suffered an incident in which secondary cooling water flooded through a broken valve and caused a number of electrical problems in the plant, resulting in a 4-day shutdown.〔(The Flooding Incident at the Ågesta Pressurized Heavy Water Nuclear Power Plant (pdf) )〕 R1, R3, and particularly the never finished R4 project at Marviken were heavy water reactors which could have been used to produce weapons grade plutonium for Swedish nuclear warheads. The Swedish nuclear weapons programme was eventually shut down, however, and Sweden signed the nuclear non-proliferation treaty in 1968.〔"Neutral Sweden Quietly Keeps Nuclear Option Open", ''The Washington Post'', 25 November 1994〕 After the partial meltdown at the Three Mile Island Nuclear Generating Station (United States) in 1979, there was a national referendum in Sweden about the future of nuclear power there. As a result of this, the Riksdag decided in 1980 that no further nuclear power plants should be built, and that a nuclear power phase-out should be completed by 2010. Some observers have condemned the referendum as flawed because people could only vote "NO to nuclear", although three options were basically a harder or a softer "NO". After the 1986 Chernobyl accident in Ukraine, the question of security of nuclear energy was again raised. In July 1992 an incident at Barsebäck 2 showed that the five older boiling water reactors had had potentially reduced capacity in their emergency core cooling systems since they started operation. Mineral wool was dislodged and ended up in the suppression pool where it clogged the suction strainers.〔http://www.nrc.gov/reading-rm/doc-collections/gen-comm/bulletins/1996/bl96003.html〕 It was classified as a grade 2 incident in the IAEA INES scale, due to the degradation of defence-in-depth. All five reactors were ordered down by the Nuclear Inspectorate for remedial action where backwash and additional strainers were installed. Most of the reactors were back in operation by next Spring, but Oskarshamn 1 remained down till January 1996 due to other work being carried out. In 1997 the Riksdag decided to shut down one of the reactors at Barsebäck by 1 July 1998 and the second before 1 July 2001, although under the condition that their energy production would be compensated. The next conservative government tried to cancel the phase-out, but, after protests, did not cancel it but instead decided to extend the time limit to 2010. At Barsebäck, block 1 was shut down on 30 November 1999 and block 2 on 1 June 2005. In June 2005, radioactive water was detected leaking from the nuclear waste store in Forsmark, Sweden. The content of radioactive caesium in the water sampled was ten times the normal value. wikinews:Radioactive leakage at Swedish nuclear waste store. In August 2006 three of Sweden's ten nuclear reactors were shut down due to safety concerns following an (incident ) at Forsmark Nuclear Power Plant, in which two out of four emergency power generators failed causing a power shortage. It was classified as a grade 2 incident in the IAEA INES scale, due to the degradation of defence-in-depth. In 2006 the Centre Party of Sweden, an opposition party that supported the phase-out, announced that it is dropping its opposition to nuclear power, at least for the time being, claiming that it is unrealistic to expect the phase-out in the short term. It said it would now support the stance of the other opposition parties in Alliance for Sweden, which were considerably more pro-nuclear than the then Social Democratic government.〔(Centre dumps nuclear deal ), The Local, 30 May 2006〕 On 17 June 2010, the Riksdag adopted a decision allowing the replacement of the existing reactors with new nuclear reactors, starting from 1 January 2011. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nuclear power in Sweden」の詳細全文を読む スポンサード リンク
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